This invention relates to asphalt-based roofing materials, and in particular to depositing protective and decorative shingle granules onto an asphalt coated sheet, for such uses as asphalt strip shingles.
Asphalt-based roofing materials, such as roofing shingles, roll roofing and commercial roofing, are installed on the roofs of buildings to provide protection from the elements, and to give the roof an aesthetically pleasing look. Typically, the roofing material is constructed of a substrate such as a glass fiber mat or an organic felt, an asphalt coating on the substrate, and a surface layer of granules embedded in the asphalt coating.
A common method for the manufacture of asphalt shingles is the production of a continuous sheet of asphalt material followed by a shingle cutting operation which cuts the material into individual shingles. In the production of asphalt sheet material, either a glass fiber mat or an organic felt mat is passed through a coater containing hot liquid asphalt to form a tacky, asphalt coated sheet. Subsequently, the hot asphalt coated sheet is passed beneath one or more granule applicators which discharge protective and decorative surface granules onto portions of the asphalt sheet material.
In the manufacture of colored shingles, two types of granules are typically employed. Headlap granules are granules of relatively low cost used for the portion of the shingle which will be covered up on the roof. Colored granules or prime granules are of relatively higher cost and are applied to the portion of the shingle that will be exposed on the roof.
To provide a color pattern of pleasing appearance, the colored portion of the shingles may be provided with areas of different colors. Usually the shingles have a background color and a series of granule deposits of different colors or different shades of the background color. A common method for manufacturing the shingles is to discharge blend drops onto spaced areas of the tacky, asphalt coated sheet. Background granules are then discharged onto the sheet and adhere to the tacky, asphalt coated areas of the sheet between the granule deposits formed by the blend drops. The term xe2x80x9cblend dropxe2x80x9d, as used herein, refers to the flow of granules of different colors or different shades of color (with respect to the background color) that is discharged from a granule blend drop applicator onto the asphalt coated sheet. The patch or assemblage of the blend drop granules on the asphalt coated sheet is also referred to as the xe2x80x9cblend dropxe2x80x9d.
One of the problems with conventional granule application equipment is that it depends on mechanical movement to discharge blend drops onto the moving asphalt coated sheet. Usually the granules are fed from a hopper by means of a fluted roll from which, upon rotation, the granules are discharged onto the sheet. The roll is ordinarily driven by a drive motor, and the roll rotation is started and stopped by means of a brake-clutch mechanism. The requirement for mechanical action has inherent limitations which prevent a very precise beginning and ending to the blend drop. Also, once the mechanical action takes place, there is a short time lag as the inertia of the granules is overcome. Consequently, there is a limit to the sharpness of the blend drops on the shingle. As shingle manufacturing lines go up in speed, the lack of sharpness is accentuated and the distinction between the blend drop granule deposits, and the background color becomes fuzzy. The lack of sharpness puts a severe limitation on the kinds of patterns and color contrasts that can be applied to shingles at high production speeds.
A known granule depositing method designed to overcome the sharpness problem of conventional granule applicators is shown in U.S. Pat. No. 5,795,389 issued to Koschitzky. The Koschitzky reference discloses an auxiliary belt traveling above the asphalt coated sheet. A series of rectangular openings in the belt allow granules dropping on the belt to drop through the belt to form straight edge blend drops because stray granules will not pass through the belt, but will be carried away. However, the granules being dropped onto the asphalt coated sheet in this method have zero forward velocity, and considerable bouncing and scattering of the granules, and therefore fuzzy edges, would be expected. Further, the apparatus in the Koschitzky patent does not offer any opportunity to react to changes in the speed of the asphalt coated sheet. The length and spacing of the blend drops from the Koschitzky transfer belt are fixed by the length and spacing of the openings in the belt, and the openings cannot be changed during production without changing the belt.
In an alternative embodiment, the Koschitzky reference discloses that the auxiliary belt includes an upper flight and a lower flight, with the upper flight travelling in a direction opposite that of the asphalt coated sheet. At the upstream end of the auxiliary belt (i.e., upstream with respect to the movement of the asphalt coated sheet) the upper flight of the auxiliary belt turns around a belt roller to form the lower flight. A retaining conveyor is wrapped around the upstream end of the auxiliary conveyor to keep the granules from flying about as the granules are turned into a downward direction. The granules of each of the patches are dropped vertically straight down onto the asphalt coated sheet to form blend drops. After the blend drops are applied to the asphalt coated sheet the background granules are applied to form a granule coated sheet, which is then cooled and cut into individual granule coated shingles.
While the retaining conveyor disclosed in the Koschitzky patent is able to successfully turn down the granules from the auxiliary conveyor, as the vertically moving granules make impact with the moving asphalt coated sheet, a significant portion of the granules bounce on the sheet, landing downstream and thereby causing fuzzy blend drop edges rather than sharply defined leading and trailing edges for the blend drop. This problem is magnified when the asphalt coated sheet is operated at high speeds. Also, in a manner similar to the first embodiment disclosed in the Koschitzky patent, there in no opportunity to react to changes in the speed of the asphalt coated sheet, and the length and spacing of the blend drops are fixed by the length and spacing of the openings in the belt, which cannot be changed during production without changing the belt.
U.S. Pat. No. 5,814,369 to Bockh et al. discloses another blend drop granule applicator having an applicator roll positioned to rotate directly above a moving asphalt coated sheet. Granules corresponding to a desired blend drop are deposited onto the applicator roll at the top of the rotation, and when the applicator roll rotates approximately 180 degrees the blend drop falls off onto the asphalt coated sheet when the blend drop reaches the bottom of the rotation. A media retaining belt engages the applicator roll, contacting and wrapping around the applicator roll to hold the blend drop granules on the surface of the applicator roll until the applicator roll rotates about 180 degrees. At the point where the media retaining belt stops contacting or becomes disengaged from the applicator roll, the blend drop granules are released to drop onto the moving asphalt coated sheet to form the blend drop. The Bockh et al. patent states that the distance that the granules fall from the applicator roll to the asphalt coated sheet should be minimized. The Bockh et al. patent further states that the linear speed of the applicator roll should be synchronized with that of the moving asphalt coated sheet so that the granules can be dropped precisely in the desired pattern.
A limitation with the process disclosed in the Bockh et al. patent is that it only works at relatively low line speeds, such as, for example, below 300 feet per minute. At higher line speeds one would expect the granules to fly out of the pockets due to centrifugal force. Further, since the pockets are fixed on the fixed size drum, there is no flexibility to alter the cycle pattern without replacing the drum. The drum can be sped up to accommodate increases in the speed of the asphalt coated sheet, but the length of spacing between blend drops cannot be changed while maintaining the drum speed equal to the speed of the asphalt coated sheet.
It would be advantageous if there could be developed a shingle blend drop technique that enables blend drops to be accurately placed on a moving asphalt coated sheet with sharply defined edge definition at high operating speeds. Ideally, the technique would allow the size and shape, i.e., the appearance, of the blend drop to be identical to the desired appearance regardless of the speed of the moving asphalt coated sheet. Further, the length and spacing of the blend drops in the machine direction should be independently adjustable without physically changing the equipment.
The above objects as well as other objects not specifically enumerated are achieved by a method of applying blend drop granules to an asphalt coated sheet including moving an asphalt coated sheet in a machine direction, depositing a blend drop of granules on a blend drop conveyor that is moving at a first speed, changing the speed of the blend drop conveyor to a second speed that is closer to the speed of the moving asphalt coated sheet than is the first speed, and releasing the blend drop from the blend drop conveyor for contact with the asphalt coated sheet.
According to this invention there is also provided a method of applying blend drop granules to an asphalt coated sheet including moving an asphalt coated sheet in a machine direction, depositing a blend drop of granules on a blend drop conveyor that is stationary, accelerating the blend drop conveyor to a speed that approximates the speed of the moving asphalt coated sheet, and releasing the blend drop from the blend drop conveyor for contact with the asphalt coated sheet.
According to this invention there is also provided a method of applying blend drop granules to an asphalt coated sheet including moving an asphalt coated sheet in a machine direction, providing a blend drop conveyor that has a surface having a plurality of cells for containing the blend drop granules, depositing a blend drop of granules on the blend drop conveyor, and releasing the blend drop from the blend drop conveyor for contact with the asphalt coated sheet.
According to this invention there is also provided apparatus for applying blend drop granules to an asphalt coated sheet, where the apparatus includes a blend drop conveyor for receiving blend drop granules and releasing the blend drop granules for contact with the asphalt coated sheet. The blend drop conveyor is positioned above the asphalt coated sheet, and the blend drop conveyor has a driving means for driving the conveyor. A blend drop applicator is positioned above the blend drop conveyor for feeding blend drop granules to the blend drop conveyor. A controller is adapted to send a signal to the driving means to drive the blend drop conveyor at a first speed when the blend drop applicator is feeding blend drop granules to the blend drop conveyor, and adapted to send a different signal to the driving means to drive the blend drop conveyor at a second speed after the blend drop granules are positioned on the blend drop conveyor.
According to this invention there is also provided apparatus for applying blend drop granules to an asphalt coated sheet, where the apparatus includes a blend drop conveyor for receiving blend drop granules and releasing the blend drop granules for contact with the asphalt coated sheet. The blend drop conveyor is positioned above the asphalt coated sheet, and the blend drop conveyor has a plurality of cells for containing the blend drop granules.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings.